1. Field of the Invention
The present invention relates to an apparatus for low-temperature plasma treatment of a sheet material such as a cloth and a film for improving the quality of the product obtained, particularly by controlling the temperature of the material in the course of treatment and including a feeding device of electric energy to the apparatus.
2. Description of the Related Art
It has been developed recently to subject a sheet material such as a long cloth and a long film produced commercially to low-temperature plasma treatment by transporting said sheet material through a reaction chamber in which low-temperature plasma is generated for improving the quality of the material treated. The mechanism of the conventional apparatus for low-temperature plasma treatment of a sheet material is to supply a gas for generating plasma into a reaction chamber provided with an electrode for generating plasma and to feed high frequency with a frequency of, for instance, 13.56 MHz to the electrode for generating low-temperature plasma in the reaction chamber. By transporting a sheet material through gas atmosphere thus excited with low-temperature plasma, the plasma treatment in object can be accomplished.
However, in such a conventional apparatus for low-temperature plasma treatment of a sheet material, there have been shortcomings in such points as the efficiency of generating low-temperature plasma, the quality low-temperature plasma gas generated and its utilizing efficiency. Namely, while it is possible to generate low-temperature plasma in the reaction chamber, low-temperature plasma gas utilized practically for the treatment of a sheet material passing through the reaction chamber is only a part of the gas generated and the remainder of the gas is usually abandoned in vain, thus deteriorating the utilization efficiency of the plasma or, in other words, the utilization efficiency of electric power for generating high frequency. Further, in a conventional apparatus for low-temperature plasma treatment in which a long sheet material is transported continuously therethrough a large amount of external atmosphere (air) is penetrated into the reaction chamber unavoidably due to the incompleteness of the seal mechanism thereof and the amount of by-product gas contaminated therein is increased unavoidably. As a result, there is a drawback that a large amount of by-product gas is absorbed on the surface of the sheet material, thus lowering the efficiency of treatment.
Moreover, when there occurs a temperature change in the course of continuous low-temperature plasma treatment of a sheet material, particularly in the case of a textile product such as a cloth, the quality of the textile product after treatment is deteriorated due to the fluctuation of the treating temperature thereof, and in some instances when the temperature of the textile product is apart from the desirable treating temperature, the treatment in object cannot be done satisfactorily. Therefore, it is desirable in such a case that the temperature of a textile product passing through the low-temperature plasma gas atmosphere in a reaction chamber is constant at a suitable prescribed temperature through the period of treatment. In such a reaction chamber, however, such parts as guide rolls, electrode plates and walls in a reaction chamber are heated naturally in the progress of the treatment, and the heat thus accumulated is transmitted directly and/or indirectly to the textile product unavoidably. As a result, the temperature of the textile product is also elevated, and accordingly, the low-temperature plasma treatment thereof becomes non-uniform, causing the difficulty that the treatment in object cannot be attained satisfactorily.
Separately, in subjecting a broad sheet material (for instance with a width of 90 to 180 cm) to low-temperature plasma treatment, a large size reaction chamber with a large size electrode is necessitated, and the leakage of plasma is easily caused to occur unavoidably due to the discharge between the feed wire and the electrode, causing a shortcoming that a large amount of energy must be consumed. For the purpose to depress such an energy loss, it is effective to transmit electric current by connecting a high frequency generating device outside of the reaction chamber and an electrode for generating low-temperature plasma in the reaction chamber with the use of a shielded wire (i.e., coaxial cable). However, since the insulating layer around the lead wire of a shielded wire comprises usually a resin with low heat-resistivity such as polyethylene, the heat accumulated in said electrode (to about 100.degree. C.) during treatment is transmitted to said shielded wire for heating it, and consequently, there occurs a difficulty that the insulation of said shielded wire is frequently broken due to the fusion of the insulating layer thereof which is consisted of a low heat resistive material such as polyethylene.